With iOS devices, you have the option of using a hardware interface for MIDI communication. Lemur Editor and OSC communication is not possible through hardware interfaces. You have a choice between three types of iOS MIDI adapters, as well as Network MIDI over the Apple Sync Cable. In all cases, follow the instructions that come with your particular hardware device to plug it to the tablet.
Once the device is connection, configuring MIDI ports in Lemur is simple. Go to the Settings / More Settings page and select the ports in MIDI Target 0 (or, for advanced users, whichever target your template is using).
The first type, and most highly recommended, is devices that are both USB and CoreMIDI Compliant. That means that the device plugs into your iPad at one end, and plugs into a USB port of your laptop at the other end. These devices provide a direct connect between your iPad and laptop.The best in this category are the iConnect MIDI line of products, such as iConnectMIDI2+ and iConnectMIDI 4+. The Alesis iO Dock unfortunately does not support SysEx messages, thus making it incompatible with many MIDI apps (including LiveControl 2) and hardware synthesizers. The Behringer iS202, although untested, appears to be a working model and its specs do specifically mention SysEx support. For any of these devices, the setup looks like this: iPad → iConnectMIDI2+ → Laptop.
Note: iConnect MIDI devices are very powerful and allow for complex routing. Check the configuration in the iConnect device itself (using the app or desktop software) to make sure the MIDI ports are properly enabled and routed to each other.
The second type of iOS MIDI adapter standard 5-pin MIDI cables coming from your iPad. This is very useful if you want to use your iPad to control a hardware synthesizer, but if you want to connect to your laptop then you will additionally need a soundcard with physical MIDI ports or a MIDI interface. A good example of this type of adapter is the iRig MIDI II, which plugs into the iPad at one end, and has MIDI cables at the other end. A typical setup in this case would be: iPad → iRig MIDI II → Audio/MIDI Interface → Laptop.
The third type of connection relies on Apple's Camera Connection Kit. That is a small adapter that plugs into your iPad and simply has a female USB socket. You can then connect any Class Compliant audio/MIDI interface (Class Compliant means that you don't need to install any drivers, it just works). If the goal is to connect the iPad to the laptop, then most elegant solution is to use a simple 1in/1out USB to MIDI adapter, such as the ESI Midi Mate II, M-Audio Uno or the iConnectMIDI1. As with type 2 above, you still need to connect the physical MIDI cables from the interface to another interface on your computer. A setup in this case could resemble the following: iPad → CCK → M-Audio Uno → Audio Interface → Laptop.
As you can see, the first option is the simplest and involves the least amount of things, whereas the second and third option require more cables and connections. For any serious musician using an iPad and MIDI apps, we highly recommend the iConnectMIDI2+ and iConnectMIDI4+.
Finally, if you have Personal Hotspot enabled (described in the 'OSC over Cable' section above), you may be able to connect with Network MIDI over the Apple Sync Cable. This one hasn't been tested in-house, but in theory it should work for any CoreMIDI app or for apps with custom MIDI protocols such as the Lemur Daemon.